The biological activity of estriol

Summary

The purpose of study was investigation of the biological action of estriol, which is considered slightly active, on the mammary gland. The experiments were made on suckling female rats, which were given injections of chorionic gonadotropin in a dose of 150 i.u. daily during a period of 15 days and, simultaneously estradiol, estron or estriol in a dose of 5 μg. It has been found that under such experimental conditions estriol causes the same degree of development of the mammary glands as do estradiol and estron. It has been inferred from these findings that estriol has a high biologic activity with regard to the mammary glands. This fact throws light on a number of paradoxical clinical phenomena.